1) Field of the Invention
The present invention relates to a barrier rib formation or forming composition for manufacturing a plasma display panel. More particularly, the present invention relates to a barrier rib forming composition for manufacturing a plasma display panel which is capable of hydrogen bonding, and contains a mixed solvent including a second solvent with a high boiling point and a low vapor pressure to enable rapid formation of barrier ribs.
2) Description of the Related Art
With the advent of the new century, plasma display panels (referred to as “PDPs”) have been standing at the forefront of the large-sized display market.
The PDP is representative of a flat display device along with a field emission display (FED) and a liquid crystal display (LCD), and has merits that in that it has a simple structure that makes it easier to manufacture, an excellent light efficiency including high brightness and high light emission, a memory function and a wide viewing angle of greater than 160°, and can display a large screen of more than 40 inches.
Generally, a PDP has the construction as shown in FIG. 1.
That is, the PDP comprises: a rear substrate 1 having an address electrode 11 mounted thereon; a lower dielectric layer 12 coated on top of the rear substrate 1 at a predetermined thickness to form a wall charge; barrier ribs 3 formed on top of the lower dielectric layer 12 to separate each discharge cell; a fluorescent material 4 excited with light generated by plasma discharge to emit light; transparent sustain electrodes 21 formed on the bottom of a front substrate 2; an upper dielectric layer 22 coated on the bottom of the front substrate 2 at a predetermined thickness to form a wall charge; and a protective layer 23 coated on the bottom of the dielectric layer 22 to protect the upper dielectric layer 22 from sputtering by discharge. In the PDP thus-constructed, when a predetermined driving voltage (e.g., of 200V) is applied to the address electrode 11 and the sustain electrode 21, plasma discharge occurs in the discharge cell by electrons emitted from the address electrode 11. More concretely, electrons emitted from the electrode causes a second electron emission while ionizing the atoms in the gas selected from the group consisting of helium (He), neon (Ne), argon (Ar) or a mixture thereof sealed in the discharge cell by friction with the atoms of the gas. The second electrons sequentially ionize the atoms while repeating the friction with pseudo atoms. That is, this leads to a state of electron amplification, at which electrons and ions are doubled, i.e., a so-called avalanche state. The light generated in this procedure excites the fluorescent material 4 put into the discharge cell, and the molecules of the fluorescent material 4 in an excited state are transited to a ground state again to emit light of three primary colors of red (hereinafter, “R”), green (hereinafter, “G”) and blue (hereinafter, “B”) according to the type of fluorescent material. This light of R, G or B proceeds to the front substrate 2 made of glass via the protective layer 23, the upper dielectric layer 22 and the transparent sustain electrode 21 to display characters or graphics. Meanwhile, the barrier ribs 3 are formed in a stripe shape or the like to separate each discharge cell and reflect the light emitted from the fluorescent material 4 toward the front substrate 2.
Therefore, in the manufacture of a PDP, the formation of barrier ribs is a very important process, and in order to apply the PDP to a high picture quality display apparatus, barrier ribs are made higher in definition, and a high aspect ratio is required.
As shown in FIG. 2, several methods of forming barrier ribs have been developed and used.
First, the methods are roughly divided into a paste application method and a green sheet application method.
The paste application method is classified into a technique of forming barrier ribs by a sanding method after applying a barrier rib forming paste to a rear substrate of glass by screen printing or table printing and drying it and a technique of forming barrier ribs by a chemical etching method after applying a barrier rib forming paste on a rear substrate of glass by table printing and drying it. However, the paste application method has a technical difficulty in that the larger the screen is, the more difficult it is to uniformly apply the paste. Non-uniform application of the paste results in the formation of non-uniform discharge cells by the formation of non-uniform barrier ribs, which ultimately provides a non-uniform screen. Further, the sanding method has a demerit that it is impossible to form barrier ribs of various shapes.
The green sheet application method is a technique of forming barrier ribs by a sanding method or chemical etching method after firstly molding a paste into a green sheet having a predetermined width, thickness and length by using a thick film coater properly constructed, transferring the green sheet and sintering it. Such a technique of using a green sheet is a technique suitable for the manufacture of a PDP, a large-sized display, and allows the PDP to have a uniform thickness because the green sheet is formed first and thus results in the formation of uniform discharge cells by the formation of uniform barrier ribs, which ultimately provides a uniform screen.
One of the many difficulties in the technique of using a green sheet is the problem of sintering. That is, a large amount of air bubbles may be generated in a green sheet plastic body during sintering in the procedure of forming barrier ribs by a sanding method or chemical etching method after transferring the green sheet on the lower dielectric layer 12 of the rear substrate 1 and sintering it in order to increase the speed of production of barrier ribs. These air bubbles have a size ranging from several microns (μm) to several hundreds of microns (μm), and if these air bubbles are present in the portions where barrier ribs should remain after sanding or etching, which is the process of forming barrier ribs, barrier ribs cannot be formed. The non-formation of barrier ribs leads to the non-formation of discharge cells, which are the base of pixels, to cause defective pixels and poor picture quality. Whether air bubbles are formed or not during sintering are dependent upon the composition and physical properties of a barrier rib forming paste.